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19 Cards in this Set

  • Front
  • Back

When and why does steel undergo a brittle fracture?

At reduced temperatures, steel becomes a brittle material, rather than a ductile one. This means that only a small amount of energy is needed to create a fast fracture, leading to a potentially catastrophic failure.

This can occur in large welded structures, in low toughness steels under high tensile stress.

Page 1-9

Brittle fracture is common in situations where the steel is under large tensile stresses, has a low toughness and/or a high strain rate. What are some of the factors that can cause these situations to occur?

- Low temp (reduces toughness)

- thick plate and/or rigid joints (high restraint)

- repeated loading (fatigue, causes cracks and stress concentrations)

- residual stresses from welding and forming

Page 1-12

Names some types of steel:

- Carbon-Manganese Constructional Grade

- Weathering (WR Grade) Steels

- Mild Steels

- HSLA Steel

- Quneched and Tempered Steels

- Martensitic Steels

- Ultra-High Strength Maraging Steels

- Tool and Die steels

- Water Hardening Tool Steels

Page 1-16, 1-17, 1-21, 1-24, 1-27, 1-28, 1-39, 1-42, 1-45

Describe the properties of a C-Mn (Carbon Manganese) Steel

- Low carbon content

- Good toughness and weldability

- 350-400 MPa

- Used for structural application

Page 1-16

Compare weathering grade steels and C-Mn Steels.

- Addition of Copper (Cu) and Chromium (Cr) provides better atmospheric corrosion resistance

- Strength is approximately the same

- Does not need painting

- Particularly used for exposed structural elements

Page 1-17

What are the three primary criterion for the selection of steels?

- Strength

- Toughness

- Weldability (Assessed with carbon equivalent)

Page 1-19

What is the difference between High-Strength Low Alloy (HSLA) steels and C-Mn steels?

- A higher strength (up to 500 MPa)

- About the same weldability

- Better mechanical properties under thermo-mechanical processing

- Difference comes about because of small addition of alloying elements (Cr, Ni, Ti)

Page 1-24

Where are quenched and tempered (Q+T) steels used?

- They are used when weight savings are desired, by having high hardness (300-500 BHN) or high strength (800-1000 MPa)

- Have good weldability

- Examples include: high performance components, military hardware and mining equipment

Page 1-27

Why is tempering necessary in Q+T steels?

Tempering is necessary to increase the ductility of the steels. If not tempered, the steels will be very brittle and fracture easily.

What advantage does face hardening have for martensitic steels in terms of impact protection?

The hard face does not get unduly deformed by an impact, and the more ductile steel behind the face can absorb the energy of the impact.

Page 1-36

Name some characteristics of martensitic steel

- High strength and hardness

- Also quite tough and fracture resistant

- Harden just the surface, or the whole way through the thickness

- Requires care in fabrication

How is face-hardened armour produced?

Local flame heating and immediate water quenching is used to harden outer faces.

Page 1-36

What are ultra-high strength maraging steels about?

- Fully martensitic with alloying elements to give age hardening properties (Mo, Ti, Cu)

- Gives considerable weight savings

Page 1-39

How are tool and die steels hardened?

They are heat-treated to produce superior mechanical properties (high strength, wear resistance, hardness, impact resistance, etc.)

Which group of steels is used for 'cold' applications?

Water hardening steels

Page 1-45

Which group of steels is used for hot working applications?

Hot Worked steels

Page 1-46

What makes high speed steels good for use as high-speed cutting tools?

They don't soften as much at high temperatures and have a good wear resistance. They are heat-treated to have a high hardness, but a reduced toughness.

Page 1-47

Name the five types of cast iron and some of their properties

- Gray– High C allow, low strength and ductility

- White– Hard brittle alloy with massive Fe3C content

- MalleableIron – heat treated white iron with increased ductility

- Ductile– Similar to malleable iron except S and Mg are added to further increaseductility

- Alloy –Usually with gray or white irons to improve hardness or corrosion resistance

How does the fracture resistance of cast irons compare with other steels?

It is much lower.

Page 1-59